The ultimate objective of this research is to derive a faithful and economical representation of visual processes. The basic approach is to separate the visual processes into smaller and simpler functional units for study. The method depends on exploiting a nonlinear process in the retina that partitions the visual system into separate compartments in a way that allows separate investigation of each compartment, and provides a reference point in the sequence of processes. The present proposal is to continue to exploit this and related methods and to extend the approach into new regions of the visual system. Specifically, the aims are to: test spatial and temporal interactions preceding and following the nonlinear stage under different states of adaptation; use the apparent motion created by relative motion of an afterimage and a superimposed stimulus to measure eye movements and their effects on visual sensitivity, and compare the results with a theoretical analysis of the effects of linear and oscillatory eye movements on visual sensitivity; measure the size of cones containing different pigments; extend the work to exploit the next nonlinearity in the system through monocular and binocular interactions between the neural representations of patterns cast onto the retina and signals produced within the visual system by nonlinear processes.